Stickler for the rules is in place to welcome returning knight (6)
I believe the answer is:
purist
'stickler' is the definition.
(I've seen this before)
'place to welcome returning knight' is the wordplay.
'place' becomes 'put' (synonyms).
'to welcome' indicates putting letters inside (in sense of 'inviting in').
'returning' is a reversal indicator.
'knight' becomes 'sir' (a knight has the title Sir).
'sir' backwards is 'ris'.
'put' placed around 'ris' is 'PURIST'.
'for the rules is in' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for purist that I've seen before include "scrupulous" , "Over-fastidious person" , "Fastidious person" , "One who insists on precision and correctness" , "Pedantic type" .)